The case for polylactic acid as a commodity packaging plastic

Polylactide, sometimes called polylactic acid (PLA), meets many requirements as a packaging thermoplastic and is suggested as a commodity resin for general packaging applications. Its general physical properties and melt processing ease are similar to conventional packaging resins. PLA slowly degrades by hydrolysis in even a slightly moist environment over a period of several months to a year to environmentally-friendly products, which, in turn, biodegrade to carbon dioxide, methane, and water. PLA is a clear, colorless thermoplastic when quenched from the melt and is similar in many respects to polystyrene. When plasticized with its own monomers, PLA becomes increasingly flexible so that a continuous series of products can be prepared that can mimic PVC, LDPE, LLDPE, PP, and PS. Degradation is increased with increasing plasticizer, and shelf life is favored by decreasing plasticizer content and/or orientation. Orientation also substantially improves tensile strength, modulus, and heat stability. A general rationale for the commercial development of PLA is presented.